Impact theory is the idea that the moon was formed by a collision between the Earth and another body.
The capture theory is the idea that the moon formed somewhere else in the solar system. The theory proposed that the moon was just an asteroid pulled into orbit by the Earth.
Co-formation is a theory that proposes that the Earth and the moon formed around the same time as each other from a primitive solar nebulae.
The answer to your question then is CAPTURE THEORY.
